Shock Talk: The Drag Racing Shock Absorber Top 10 Tips

Hardcore drag racing vehicles are among the most well-oiled machines in motorsports, with components and their settings all intricately linked into a finely tuned combination which, when off even by the most minute of adjustments, can make or break those few seconds of glory. While it would be difficult to pinpoint the single most important adjustable component on a race car, the front and rear shocks certainly play into the discussion, and we’ve laid out a number of different topics regarding shocks in drag racing in a top 10-esque list and taken our questions to the experts to get their thoughts, experiences, and viewpoints.

Among the manufacturers we reached out to include some of the most respected names and individuals in the industry, including Chris Alston Sr. with Varishock, AFCO Drag Racing Product Manager Eric Saffell, QA1 Sales and Support Specialist David Goldie, and Dimitry Zhukovsky, part of the engineering team at Strange Engineering.

1) What is the difference between mono-tube and twin-tube drag shocks and how does a racer choose between them?

Twin tube racing shocks are a relatively new technology that – contrary to popular belief that there are two tubes inside – have a piston riding up and down on a tube inside of the reservoir. In a traditional mono tube, the piston rides on the reservoir body itself.

“A mono tube shock allows for a larger piston, but that’s not necessarily better for drag racing,” says Alston. “There’s no particular reason to use one over the other. What really matters is whether the valving right for your application. In drag racing, you don’t have the heat problems of other forms of racing, so a lot of these gazillion-tube shock technologies are a moot point.”

According to Saffell, one of the biggest physical differences between the mono and twin-tube shocks is the way in which a mono-tube shock dampens more effectively to control tire shake. “A mono-tube shock is a nitrogen-charged shock that picks up movements in the suspension a little more effectively and does a better job of dampening. The nitrogen also helps with cavitation. It’s all about matching the car up to the right shock, and for heads-up racers with power adders, the twin-tube works, but the mono-tube is the best product available.”

2) How does a racer know when he needs a non-adjustable, single adjustable, or double adjustable shock. Is this based on ET, horsepower, or other factors? How do you help a racer choose the correct shock type?

Adjustability is a priceless asset for a drag racing vehicle, and the reason for that is simple. Based on weight, horsepower, and performance, an infinite number of variables play into the proper valving of a shock, and finding the optimum non-adjustable shock would be like purchasing a winning lottery ticket.

Adjustable shocks allow for changes in the shock to compliment a specific combination and further adjust based on track conditions. As many of you know, single adjustables allow for optimization of the compression, while double adjustable give you control over the compression and rebound, essentially providing you the keys to the shocks and their functionality in both departments. Naturally, adjustable shocks have a higher cost, but the ability to have control is worth its weight in gold.

A detailed look at the single and double adjustable shock knobs on the Varishock shock absorbers. Single adjustables allow for tuning of the rebound, while the double gives you control over both variables independent of one another.

A diagram outlining the adjustments necessary to tune compression and rebound on the Varishock units.

“Every drag racer needs a double adjustable shock,” the straight-shooting Alston states. “Whether it’s fast, slow, real fast, or real slow. And the reason is because if you want to be able to get your car to work its best, you need to be able to independently adjust the compression and rebound.”

3) How do you build a baseline with adjustable shocks? Where do you start?

Does he want it to squat, or separate the rear end? Does he want it to do a wheelstand for weight transfer or keep the front end planted? – Dimitry Zhukovsky

For the street and strip folks out there utilizing single adjustable shocks, they will typically be at or around a 50/50 ratio for street use, necessitating some adjustment when going into competition mode. But for the hardcore drag racers with both adjustments at their fingertips, QA1’s Goldie suggests, “A rebound setting that’s softer than the compression on the nose for optimum weight transfer, and vice versa in the rear to control the initial hit on the suspension upon launch.”

Explains Zhukovsky, “The first thing that we need to know is the weight of the car and how fast it’ll run. From there, we need to figure out what the customer wants his chassis to do. Does he want it to squat, or separate the rear end? Does he want it to do a wheelstand for weight transfer or keep the front end planted? With this information in hand, from our experience and the behavior of the chassis, we can make recommendations on the shock valving to get a customer headed in the right direction.”

4) Most racers seem to understand how to adjust front struts or shocks. How do you adjust and tune your rear shock for compression and rebound? What process do you recommend a racer follow?

Every race car, even those that a chassis builder constructs to be identical to another, has it’s own specific DNA. There are baselines to follow that shock manufacturers and chassis builders can dial in, but each car is going to require its own fine tuning to gain the utmost in performance. And how do you accomplish this? By making runs, studying how the car reacts and performs, and adjusting accordingly. This can identified through feel, sight, videotape, and if you have prior data to compare with, can even see the positives or negatives of your adjustments on the time slip.

“You basically have to watch the tire and see how hard or how soft you hit the tire, making sure you hit it hard enough to plant it, but not so hard that you flatten it out,” says Goldie. “A video is the best way of watching first hand how it happens, because it happens so quickly that its hard to judge.”

The best way to dial in the rear shocks for compression and rebound is simply by watching how the tire reacts at the hit. This can be accomplished by sight or through video and/or photographs.

Goldie continued, “Generally, the higher the setting, the faster it’ll roll until it spins the tires. That’s a good rule of thumb if you want some sort of gauge, because the suspension moves the least amount, using the least amount of energy, at higher settings. If it’s too firm, it’ll spin the tires rather than planting them.” Slow motion video capture or simply stop motion frames from a typical video camera make an excellent tool for viewing tires on the hit, and the reason why racers from Top Fuel to sportsman bracket racers use them.

5) Some racers mount their rear shocks in stock locations, some behind the axle, some at angles. Is the mounting location important?

At some point in our early education of suspension systems, we’ve all crawled under a car and seen the shocks mounted above and below the axle centerline or at angles or other non-traditional layouts, and wondered what the reason or the secret is. But the secret really is simply in the packaging of the suspension. Aside from third and fourth generation Camaro’s, it’s rare to see the shocks mounted in front of the axles, but from there, the angles and mounting locations can differ, but and each varying shock mounting layout will affect its valving.

Shown here is one of Chris Alston’s Chassisworks’ rear clips with the shocks angled slightly inward at the top. The angle of shocks is largely to do with packaging and tire size, but most manufacturers prefer to see the shocks mounted straight up and down in hardcore drag racing applications.

At one time, it was common to see cars with the shocks mounted in front of the axle for space reason, but as race cars have become narrower and tires have become wider, they’re almost always found behind the axle today. Chassis builders also used wider bottom shock mount to create a wider stance – and an angled shock position – to reduce body roll, but with the advent of stronger anti-roll bars, such mounting positions aren’t near as common.

Shocks work best straight up and down, and in general, you want to have them spread out as wide as you can for stability, but you’ve got to work around what the size of the tire will allow you. – David Goldie

These days, all tricks aside, the mounting point for shocks is typically based on tire clearance issues.

“Shocks work best straight up and down, and in general, you want to have them spread out as wide as you can for stability, but you’ve got to work around what the size of the tire will allow you,” Goldie explains. “Mounted straight up and down, you don’t have to worry about side load on the shock or run them at an increased rate because the shocks are at an angle.”

Saffell agrees, stating, “We like to see the shocks straight up and down for a 1:1 relationship to keep from having to compensate with the shock settings. Although there was a trend some time back to mount them in front of the axle, it’s widely accepted now for them to be behind the axle.”

6) Do drag racing shocks wear out? How many runs or passes can a shock run before it’s replaced? How do you know?

The simple answer to this question is yes, drag racing shocks do wear out. Anyone with a race car should know that. But determining their life span and when they’re due for servicing is something that many racers don’t learn until their 60-foot times fall off the planet, or worse.

“Most people don’t think a shock absorber is worn out until the oil leaks out of it,” Alston says. “But there are a multitude of things that can happen to them and the oil not leak out.” And according to Alston, builder error often leads to shorter lives for a shock, with incorrect mounting points that bind, top, or bottom them out as they go down the racetrack. “I’d say as many as 95 percent of shocks that no longer work are caused by shoddy installation.”

According to each of the sources that we spoke with, its’ recommended to send your shocks in after a seasons worth of passes – before they start leaking – to ensure that they’re in optimum working order.

In general, and as both Alston and Goldie agree, your shocks should be sent in annually for a dyno test to ensure they’re still at optimum health. A shock dyno is the single best way to check the functionality of a shock. “There’s no gauge that says for sure when they’re worn out, but having them serviced annually would probably be the best thing to do,” says Goldie. “Some guys never touch them; they bolt them on the car and they’re ten years old and leaking and they don’t even know it because the wearing process is so gradual. A racer may or may not be able to notice it, but if he bolted on a brand new set, he certainly would.” If you’ve got a couple hundred passes on your shocks, now may be the time to send them in for a once-over.

7) What about towing? We’ve heard towing wears out shocks super fast. Is there any recommended way to address wear on shocks when towing?

Sidebar title

Solving The Trailer Towing Issue

Towing is the single biggest contributor to wear and tear on a racing shock. In addition to strapping the car down by the body or chassis, suspended or air-ride trailers can be a life saver, if you can afford one.

Over the course of your race car’s life, it will rack up very little mileage in comparison to a street car. But strapped down in or on your trailer, it will be subjected to hundreds or even thousands of miles each season. Pot holes, uneven pavement, and bumps in the road can be rough on your backside on a cushioned seat in a fully suspended pickup truck, so you can only imagine what its like in the trailer.

If your car is strapped down only by the tires or the axles – as most racers do – the body and chassis are still free to roam, and that means the burden of the ride falls on the suspension, and in some cases, the chassis itself.

So what can a racer do to limit the beating that their shocks take on the highway? For starters, always strap the body and/or chassis down to the trailer. In doing so, the body and chassis move with the trailer rather than independently over the hills and valleys of the roadway, keeping the shocks from having to do any unnecessary work. Some racers also dial the shocks up to stiffer levels to limit their up and down motion and restrict the car from bouncing.

Says Alston, “If your car is strapped down by the tires and you go through a pothole, the trailer comes down into the pothole, flies back out, and now the car doesn’t follow the trailer but is actually amplified by it. So the car actually bounces a greater percentage than the trailer. You’ll beat the hell out of the suspension of a race car on a rough road without an unsprung trailer.”

This is particularly true with 4-link dragsters, not only because they’re light, but because their lengthy chassis act like a spring, and the oscillations and whipping motion they experience during travel is known to beat the chassis and shocks to pieces. For this reason, seasoned dragster owners support the car from underneath with air bags, two-by-four’s, or any other home brewed method they can come up with, and then strap the car down by the chassis.

One of the best ways to reduce travel wear on your shocks? Think air-ride trailers.

8) What is the difference between a $100 shock, a $400 shock, and a $1,500 shock?

As they say, you get what you pay for, and that statement rings loud and clear in the racing shock industry. Naturally, the difference between $100 and $1,500 spent on a shock isn’t going to net you just single or dual adjustability, but a higher grade of quality with better fit, finish, and increased tolerances on the higher-end components. The more you spend, the better the overall construction, more precise internal parts, and higher accuracy of the compression and rebound adjustments you can expect to find.

“Adjustability costs money. The more degrees of adjustability a racer wants, the more money he’ll have to spend,” explains Zhukovsky.

Although the numbers will vary by the manufacturer and the dealer, a non-adjustable twin-tube shock can be purchased for around $100, a single adjustable for $200, and double-adjustables for $250-450. Mono-tubes are more in the $1000 neighborhood, and MacPherson struts, with their complex rods and bodies, also carry a higher price range. Shocks in the $100 range sport the basic components and are built to generalized specifications, largely designed as OEM replacement or upgrade shocks.

“You get what you pay for, in that there’s a criteria that has to be met to keep that shock at that low price point,” says Saffell. As described above, shocks carrying a higher price tag bring with them improved quality of components and better tolerances, and while possibly sharing some of the technology of the lower end parts, commonly have higher-end pistons and custom valving to a customers’ requirements.

These days, virtually all drag racing shocks are made from aluminum. At one time, steel was prevalent and still remains in use in the low-grade line of shocks, but what we want to know is whether the material truly matters. And the answer is yes and no, for obvious reasons.

Aluminum is lighter than steel, and in a sport where weight matters, aluminum reigns. Aside from that element, the manufacturers we spoke with suggested that there is very little, if any, functional difference between the two materials with all other factors being equal.

A detailed diagram inside AFCO’s 37/38 Series twin-tube, double adjustable shock provides a look at the intricate parts within the body of a shock absorber. (Click for larger version)

As Zhukovsky shared with us, “Steel shocks are made from a welded DOM tubing and are generally mass produced on the same assembly line as stock or stock replacement shocks. Aluminum bodies and mounts, meanwhile, are made of machined 6061 aluminum that is more than strong enough for the shock loads. Aluminum shock bodies also make for simpler machining of the coilover threads. The rods in aluminum shocks are commonly made of carbon steel. In addition to these benefits, aluminum shocks simply look “racier.”

10) Electronically adjustable shocks: fair for the sportsman guy? Should they be legal?

Electronic shocks represent the high-end of shock absorbers for drag racing and are commonly used in Pro Stock race cars. These double adjustable shocks are typically controlled from inside the race car, and allow for changes in the compression and rebound as the car launches and heads down track for adaptable performance beyond a static shock setup.

“Electronic shocks allow the racer to generally have a firmer extension on the starting line and then soften it at a specific point in the run, making it more suitable for track imperfections,” says Zhukovsky. “If it works properly, it’s a safer shock, but it is more expensive.”

Outside of the professional classes where money exists and thousandths of a second count, each of the manufacturers we discussed this topic with were insistent that electronic shocks are simply overkill for sportsman, big money, and weekend warrior bracket racers. As finely-tuned as the machines that these competitors drive are today, the high cost of electronic shocks would seem to offer no distinct advantage over the double-adjustable shocks used in dragsters and doorslammers.

“Those [bracket] cars are so consistent now, it would be hard to make them any better than they are,” says Goldie.

On the surface and to the layman, drag racing shocks may seem like a rather simple component of a working machine, and depending on your application, they may be relatively simple and straightforward. But make no mistake that these are complex parts with an intricate, key role in the function of a race car that demand proper selection and settings. It’s our hope that this general guide to some of the top questions about drag racing shock absorbers will help you in your next purchase or with your current set of shocks to not only wring them for all they’re worth, but keep them going for seasons to come.

Article Sources

About the author

Andrew Wolf

Andrew has been involved in motorsports from a very young age. Over the years, he has photographed several major auto racing events, sports, news journalism, portraiture, and everything in between. After working with the Power Automedia staff for some time on a freelance basis, Andrew joined the team in 2010.